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Experimental C++ Features

From cppreference.net
C++
Experimental

The C++ standards committee publishes experimental C++ language and library extensions for future standardization.

Note: until 2012, these publications used the TR (technical report) format. Since 2012 ISO procedure changed to use the TS (technical specification) format.

Contents

TR/TS specifications

ISO number Name Status Links, headers
ISO/IEC TR 18015:2006 Technical Report on C++ Performance Published 2006 ( ISO store ).

Draft: TR18015 (2006-02-15).

ISO/IEC TR 19768:2007 Technical Report on C++ Library Extensions Published 2007-11-15 ( ISO store ).

Draft: N1836 (2005-06-24)
ISO 29124 split off, the rest merged into C++11.

ISO/IEC 29124:2010 Extensions to the C++ Library to support mathematical special functions Published 2010-09-03 ( ISO Store ).

Final draft: N3060 (2010-03-06).
✔ Merged into C++17 .

Special functions (experimental), Special functions
ISO/IEC TR 24733:2011 Extensions for the programming language C++ to support decimal floating-point arithmetic Published 2011-10-25 ( ISO Store )

Draft: N2849 (2009-03-06).
May be superseded by a future TS or merged into a future revision of C++ (most recent merge proposal was N3871 ).

ISO/IEC TS 18822:2015 C++ File System Technical Specification Published 2015-06-18 ( ISO store ). Final draft: N4100 (2014-07-04).

✔ Merged into C++17 .

Filesystem (experimental), Filesystem , <filesystem>
ISO/IEC TS 19570:2015 C++ Extensions for Parallelism Published 2015-06-24. ( ISO Store ). Final draft: N4507 (2015-05-05).

✔ Merged into C++17.

Parallelism
ISO/IEC TS 19841:2015 Transactional Memory TS Published 2015-09-16, ( ISO Store ). Final draft: N4514 (2015-05-08). Transactional memory
ISO/IEC TS 19568:2015 C++ Extensions for Library Fundamentals Published 2015-09-30, ( ISO Store ). Final draft: N4480 (2015-04-07).

✔ Merged into C++17 except for invocation traits.

Library extensions
ISO/IEC TS 19217:2015 C++ Extensions for Concepts Published 2015-11-13 ( ISO Store ). Final draft: N4553 (2015-10-02). Current draft: P0734R0 (2017-07-14).

✔ Merged into C++20 (with modifications).

Constraints and concepts (experimental), Concepts , <concepts>
ISO/IEC TS 19571:2016 C++ Extensions for Concurrency Published 2016-01-19 ( ISO Store ). Final draft: P0159R0 (2015-10-22).

✔ Partially merged into C++20.

Concurrency
ISO/IEC TS 19568:2017 C++ Extensions for Library Fundamentals, Version 2 Published 2017-03-30 ( ISO Store ). Draft: N4617 (2016-11-28).

✔ Partially merged into C++17 and C++20.

Library extensions 2
ISO/IEC TS 21425:2017 Ranges TS Published 2017-12-05 ( ISO Store ). Draft: N4685 (2017-07-31).

✔ Merged into C++20 .

Ranges (experimental), Ranges , <ranges>
ISO/IEC TS 22277:2017 Coroutines TS Published 2017-12-05 ( ISO Store ). Draft: N4736 (2018-03-31). Latest draft: N4775 (2018-10-07).

✔ Merged into C++20 .

<coroutine>
ISO/IEC TS 19216:2018 Networking TS Published 2018-04-24 ( ISO Store ). Draft: N4734 (2017-04-04). Latest draft: N4771 (2018-10-08).
See also non-TS proposals
  • Standard Secure Networking - P2586R0 (2022-09-13)
  • Sender-Receiver Interface For Networking - P2762R2 (2023-10-12)
  • A proposed direction for C++ Standard Networking based on IETF TAPS - P3185R0 (2024-12-14)
  • Proposed API for creating TAPS based networking connections - P3482R0 (2024-12-14)
Networking
ISO/IEC TS 21544:2018 Modules TS Published 2018-05-16 ( ISO Store ). Final Draft: N4720 (2018-01-29).

✔ Merged into C++20 .

ISO/IEC TS 19570:2018 Parallelism TS Version 2 Published 2018-11-15 ( ISO Store ). Final draft: N4793 (2018-11-26). Post-publication draft: N4808 (2019-03-11). See also non-TS std::simd proposals below . Parallelism 2
ISO/IEC TS 23619:2021 Reflection TS Published 2021-10-11 ( ISO store ). Draft: N4856 (2020-03-02). See also non-TS proposals below . Reflection
Numerics Early development. Draft: P1889R1 (2019-12-27).
ISO/IEC TS 9922 Concurrency TS Version 2 Published 2024-10-09 ( ISO Store ). Draft: N4956 (2023-07-05). Concurrency 2
ISO/IEC TS 19568:2024 C++ Extensions for Library Fundamentals, Version 3 Published 2024-08-26 ( ISO Store ). Draft: N4948 (2023-05-08). Library extensions 3
ISO/IEC DTS 12907 Transactional Memory TS, Version 2 Early development. Draft: N4923 (2022-10-14).
ISO/IEC NP 19569 Array Extensions TS × Withdrawn. Abandoned draft: N3820 (2013-10-10).

Non-TS proposals

Name Status Links, Headers
Linear Algebra ✔ Merged into C++26 . Proposal: P1673R13 (2023-11-10).
More proposals:
<linalg>
std::execution ✔ Merged into C++26 . Proposal: P2300R10 (2024-06-28).
More proposals:
  • System execution context - P2079R8 (2025-05-18)
  • Sender-Receiver Interface for Networking - P2762R2 (2023-10-12)
  • Member customization points for Senders and Receivers - P2855R1 (2024-02-22)
  • An Event Model for C++ Executors - P2882R0 (2023-05-11)
  • Sender Algorithm Customization - P2999R3 (2023-12-13)
  • std::execution introduction - P3090R0 (2024-02-14)
  • A plan for std::execution for C++26 - P3109R0 (2024-02-12)
  • Improving diagnostics for Sender expressions - P3164R4 (2025-04-28)
  • Reconsidering the std :: execution :: on algorithm - P3175R3 (2024-06-25)
  • A sender query for completion behaviour - P3206R0 (2025-01-13)
  • finally , write_env , and unstoppable Sender Adaptors - P3284R4 (2025-05-16)
  • Fixing Lazy Sender Algorithm Customization - P3303R1 (2024-06-25)
  • A Utility for Creating Execution Environments - P3325R5 (2024-11-22)
  • When Do You Know connect Doesn't Throw? - P3388R2 (2025-04-01)
  • std :: execution wording fixes - P3396R1 (2024-11-19)
  • Enabling more efficient stop-token based cancellation of senders - P3409R1 (2024-11-17)
  • system_scheduler on Win32, Darwin and Linux - P3456R0 (2024-10-15)
  • Summarizing std :: execution :: bulk ( ) issues - P3481R3 (2025-04-16)
  • High-Quality Sender Diagnostics with Constexpr Exceptions - P3557R2 (2025-05-16)
  • optional variants in sender-receiver - P3570R1 (2025-05-19)
  • Non-Blocking Support for std::execution - P3669R1 (2025-05-17)
  • Remove std::execution::split - P3682R0 (2025-05-06)
  • Rename async_scope_token - P3685R0 (2025-05-07)
  • Rename join and nest in async_scope proposal - P3706R0 (2025-05-19)
Execution (experimental),
Execution ,
<execution>
std:: inplace_vector ✔ Merged into C++26 . Proposal: P0843R14 (2024-06-26).
More proposals:
  • inplace_vector - P0843 ( R7 ) LEWG presentation - P2925R0 (2023-06-16)
  • A direction for Vector - P3147R1 (2024-03-18)
  • An allocator-aware std::inplace_vector - P3160R2 (2024-10-15)
  • No, inplace_vector shouldn't have an Allocator - P3581R0 (2025-01-13)
  • LEWG Hagenberg presentation for P3581 . No, inplace_vector shouldn't have an Allocator - P3636R0 (2025-02-13)
  • Cross-capacity comparisons for std::inplace_vector - P3698R0 (2025-05-19)
<inplace_vector>
experimental::simd
std::datapar::simd 		✔ Merged into C++26 . Proposal: P1928R15 (2024-11-22).
The main document (TS ISO/IEC 19570:2018) is described in "C++ Extensions for Parallelism V2" above.
More proposals:
Data parallel types (experimental),
Data parallel types ,
<simd>
Contracts ✔ Merged into C++26 . Proposal: Contracts for C++ - P2900R14 (2025-02-13)
More proposals:
  • A Proposal to Publish a Technical Specification for Contracts - P2659R2 (2022-11-30)
  • Proposed Contracts TS - P2660R0 (2022-10-14)
  • Miscellaneous amendments to the Contracts TS - P2661R0 (2022-10-15)
  • Contracts for C++: Prioritizing Safety - P2680R1 (2022-12-15)
  • A proposed plan for contracts in C++ - P2695R1 (2023-02-09)
  • Proposal of Condition-centric Contracts Syntax - P2737R0 (2022-12-30)
  • Contracts for C++: Prioritizing Safety - Presentation slides - P2743R0 (2022-12-13)
  • Evaluation of Checked Contracts - P2751R1 (2023-02-14)
  • A Bold Plan for a Complete Contracts Facility - P2755R1 (2024-04-11)
  • The idea behind the contracts MVP - P2817R0 (2023-03-05)
  • Proposal of Contracts Supporting Const-On-Definition Style - P2829R0 (2023-04-13)
  • Contract violation handling semantics for the contracts MVP - P2852R0 (2023-04-24)
  • The Lakos Rule: Narrow Contracts and noexcept Are Inherently Incompatible - P2861R0 (2023-05-19)
  • Requirements for a Contracts syntax - P2885R3 (2023-10-05)
  • Contracts on lambdas - P2890R2 (2023-12-13)
  • Constant evaluation of Contracts - P2894R2 (2024-01-11)
  • Outstanding design questions for the Contracts MVP - P2896R0 (2023-08-22)
  • Contracts for C++ - Rationale - P2899R1 (2025-03-14)
  • A Principled Approach to Open Design Questions for Contracts - P2932R3 (2024-01-16)
  • An Attribute-Like Syntax for Contracts - P2935R4 (2023-11-05)
  • Contracts must avoid disclosing sensitive information - P2947R0 (2023-07-20)
  • Slides for P2861R0 : Narrow Contracts and noexcept are Inherently Incompatible - P2949R0 (2023-07-14)
  • Contracts and virtual functions for the Contracts MVP - P2954R0 (2023-08-03)
  • Contracts and coroutines - P2957R2 (2024-10-14)
  • A natural syntax for Contracts - P2961R2 (2023-11-08)
  • An Overview of Syntax Choices for Contracts - P3028R0 (2023-11-05)
  • Protection against modifications in contracts - P3071R1 (2023-12-17)
  • Remove evaluation_undefined_behavior and will_continue from the Contracts MVP - P3073R0 (2024-01-27)
  • Should ignore and observe exist for constant evaluation of contracts? - P3079R0 (2024-01-11)
  • Contracts for C++: Support for virtual functions - P3097R0 (2024-04-15)
  • Contracts for C++: Postcondition captures - P3098R1 (2024-12-11)
  • Undefined and erroneous behavior are contract violations - P3100R2 (2025-05-19)
  • Tokyo Technical Fixes to Contracts - P3119R1 (2024-05-09)
  • Contracts on virtual functions for the Contracts MVP - P3165R0 (2024-02-27)
  • Inherited contracts - P3169R0 (2024-04-14)
  • Contract testing support - P3183R1 (2024-05-22)
  • Slides for LEWG presentation of P2900R6 : Contracts for C++ - P3189R0 (2024-03-19)
  • Slides for LEWG presentation of P2900R7 : Contracts for C++ - P3190R0 (2024-03-20)
  • A response to the Tokyo EWG polls on the Contracts MVP ( P2900R6 ) - P3197R0 (2024-04-12)
  • A takeaway from the Tokyo LEWG meeting on Contracts MVP - P3198R0 (2024-03-29)
  • Why Contracts? - P3204R0 (2024-11-07)
  • The contract of sort() - P3212R0 (2024-07-03)
  • Contracts for C++: Naming the Louis semantic - P3226R0 (2024-04-12)
  • Contracts for C++: Fixing the contract violation handling API - P3227R1 (2024-10-24)
  • Contracts for C++: Revisiting contract check elision and duplication - P3228R1 (2024-05-21)
  • Making erroneous behaviour compatible with Contracts - P3229R1 (2025-02-10)
  • An alternate proposal for naming contract semantics - P3238R0 (2024-05-06)
  • A unified syntax for Pattern Matching and Contracts when introducing a new name - P3249R0 (2024-05-22)
  • C++ contracts with regards to function pointers - P3250R0 (2024-05-07)
  • C++ contracts and coroutines - P3251R0 (2024-05-07)
  • Make the predicate of contract_assert more regular - P3257R0 (2024-04-26)
  • Ship Contracts in a TS - P3265R3 (2024-05-28)
  • Approaches to C++ Contracts - P3267R1 (2024-05-22)
  • C++ Contracts Constification Challenges Concerning Current Code - P3268R0 (2024-05-07)
  • Do Not Ship Contracts as a TS - P3269R0 (2024-05-21)
  • Repetition, Elision, and Constification w.r.t. contract_assert - P3270R0 (2024-05-22)
  • Function Usage Types (Contracts for Function Pointers) - P3271R1 (2024-10-15)
  • P2900 Is Superior to a Contracts TS - P3276R0 (2024-05-18)
  • Contracts: Protecting The Protector - P3285R0 (2024-05-15)
  • Integrating Existing Assertions With Contracts - P3290R2 (2024-09-06)
  • C++26 Needs Contract Checking - P3297R1 (2024-06-21)
  • An opt-in approach for integration of traditional assert facilities in C++ contracts - P3311R0 (2024-05-22)
  • Compile time resolved contracts - P3317R0 (2024-05-22)
  • Contracts Interaction With Tooling - P3321R0 (2024-07-12)
  • Contract assertions on function pointers - P3327R0 (2024-10-16)
  • Observable Checkpoints During Contract Evaluation - P3328R0 (2024-06-14)
  • Usage Experience for Contracts with BDE - P3336R0 (2024-06-23)
  • Contracts - What are we doing here (EWG Presentation) - P3343R0 (2024-06-25)
  • Virtual Functions on Contracts (EWG - Presentation for P3097 ) - P3344R0 (2024-06-28)
  • Class invariants and contract checking philosophy - P3361R1 (2024-07-23)
  • Static analysis and “safety” of Contracts, P2900 vs P2680 / P3285 - P3362R0 (2024-08-13)
  • Contract assertions versus static analysis and “safety” - P3376R0 (2024-10-14)
  • Static Analysis of Contracts with P2900 - P3386R1 (2024-11-25)
  • Contract assertions on coroutines - P3387R0 (2024-10-09)
  • Specifying Contract Assertion Properties with Labels - P3400R1 (2025-02-28)
  • Improving the handling of exceptions thrown from contract predicates - P3417R1 (2025-03-05)
  • Contracts Implementors Report - P3460R0 (2024-10-16)
  • Standard library hardening - P3471R4 (2025-02-14)
  • Constification should not be part of the MVP ( M inimal V iable P roduct) - P3478R0 (2024-10-16)
  • Exploring strict contract predicates - P3499R1 (2025-02-09)
  • Are Contracts 'safe'? - P3500R1 (2025-02-09)
  • Slides for P2900R11 - Contracts for C++ - P3502R0 (2024-11-18)
  • P2900 Is Still not Ready for C++26 - P3506R0 (2025-01-13)
  • Violation handlers vs noexcept - P3541R1 (2025-01-07)
  • Core Language Contracts By Default - P3558R1 (2025-02-03)
  • Contract concerns - P3573R0 (2025-01-12)
  • Require a non-throwing default contract-violation handler - P3577R0 (2025-01-12)
  • Observed a contract violation? Skip subsequent assertions! - P3582R0 (2025-01-13)
  • Contracts, Types & Functions - P3583R0 (2025-01-13)
  • Contextualizing Contracts Concerns - P3591R0 (2025-02-03)
  • Initial Implicit Contract Assertions - P3599R0 (2025-02-03)
  • Contracts and profiles: what can we reasonably ship in C++26 - P3608R0 (2025-02-01)
  • Remove contracts on virtual functions for now - P3616R0 (2025-02-08)
  • Make contracts reliable by default - P3640R0 (2025-03-17)
  • Minor additions to C++26 standard library hardening - P3697R0 (2025-05-16)
Contract assertions ,
function contract specifiers ,
contract_assert ,
pre , post ,
<contracts>
Reflection The main document (ISO/IEC TS 23619:2021) is described in Reflection TS above.
More proposals:
  • Scalable Reflection in C++ - P1240R2 (2022-01-14)
  • Expansion statements - P1306R4 (2025-05-17)
  • Reflection on attributes - P1887R1 (2020-01-13)
  • Metaprogramming - P2237R0 (2020-10-15)
  • Python Bindings with Value-Based Reflection - P2911R1 (2023-10-13)
  • Reflection for C++26 - P2996R12 (2025-05-17)
  • Using Reflection to Replace a Metalanguage for Generating JS Bindings - P3010R0 (2023-10-13)
  • ABI comparison with reflection - P3095R0 (2024-02-15)
  • Function Parameter Reflection in Reflection for C++26 - P3096R9 (2025-05-15)
  • Generative Extensions for Reflection - P3157R1 (2024-05-22)
  • Syntax for Reflection - P3381R0 (2024-09-17)
  • Attributes reflection - P3385R5 (2025-05-19)
  • Annotations for Reflection - P3394R3 (2025-05-17)
  • Reflection Syntax Options Summary - P3419R0 (2024-10-11)
  • Reflection of Templates - P3420R1 (2025-01-13)
  • Reflection header should minimize standard library dependencies - P3429R1 (2024-11-29)
  • Reflection and meta-programming - P3435R0 (2024-10-14)
  • Proposed default principles: Reflect C++, Generate C++ - P3437R1 (2024-11-07)
  • Reflection on SG21 2024 Process - P3443R0 (2024-10-14)
  • A Suggestion for Reflection Access Control - P3451R0 (2024-10-15)
  • Ruminations on reflection and access - P3493R0 (2024-11-10)
  • Modeling Access Control With Reflection - P3547R1 (2025-02-09)
  • Error Handling in Reflection - P3560R1 (2025-05-19)
  • Split define_aggregate from Reflection - P3569R0 (2025-01-11)
  • Reconsider reflection access for C++26 - P3587R0 (2025-01-13)
  • Do not remove nor postpone access_context::unchecked - P3614R0 (2025-02-06)
  • std::meta::reflect_constant_ {array,string} - P3617R0 (2025-05-16)
  • Inherit std :: meta :: exception from std::exception - P3637R0 (2025-03-08)
  • Final Adjustments to C++26 Reflection - P3687R0 (2025-05-15)
Reflection (experimental)
Pattern Matching Early development. Draft P1371R3 (2020-09-15).
More proposals:
  • Pattern Matching using is and as - P2392R3 (2024-10-16)
  • Pattern Matching: match expression - P2688R5 (2025-01-13)
  • switch for Pattern Matching - P2940R0 (2022-04-18)
  • Identifiers for Pattern Matching - P2941R0 (2022-02-24)
  • A Postcondition is a Pattern Match - P3210R2 (2024-09-10)
  • A unified syntax for Pattern Matching and Contracts when introducing a new name - P3249R0 (2024-05-22)
  • A simpler notation for PM - P3332R0 (2024-06-18)
  • Slides for P2688R2 - Pattern Matching: match Expression - P3476R0 (2024-10-16)
  • Pattern Matching: Customization Point for Open Sum Types - P3521R0 (2024-12-17)
  • Pattern Matching: *variant-like* and 'std::expected' - P3527R1 (2025-01-13)
  • Pattern matching - P3572R0 (2025-01-12)
Profiles Early development.
More proposals:
  • Safety Profiles: Type-and-resource Safe programming in ISO Standard C+ - P2816R0 (2023-02-16)
  • Concrete suggestions for initial Profiles - P3038R0 (2023-12-16)
  • Core safety Profiles: Specification, adoptability, and impact - P3081R2 (2025-02-03)
  • A framework for Profiles development - P3274R0 (2024-05-10)
  • A Safety Profile Verifying Class Initialization - P3402R3 (2025-05-17)
  • Profile invalidation - eliminating dangling pointers - P3446R0 (2024-10-14)
  • Profiles syntax - P3447R0 (2024-10-14)
  • Response to Core Safety Profiles ( P3081R0 ) - P3543R0 (2024-12-17)
  • The Plethora of Problems With Profiles - P3586R0 (2025-01-13)
  • C++ Profiles: The Framework - P3589R2 (2025-05-19)
  • Contracts and profiles: what can we reasonably ship in C++26 - P3608R0 (2025-02-01)
  • Dealing with pointer errors: Separating static and dynamic checking - P3611R0 (2025-02-04)
  • Easy-to-adopt security profiles for preventing RCE (remote code execution) in existing C++ code - P3627R0 (2025-02-11)
  • A principled approach to safety profiles - P3649R0 (2025-05-19)
  • 21st Century C++ - P3650R0 (2025-03-05)
  • Note to the C++ standards committee members - P3651R0 (2025-03-06)
  • Making Safe C++ happen - P3700R0 (2025-05-19)
  • What are profiles? - P3704R0 (2025-05-19)
Statistics Early development.
More proposals:
Graph Library Early development.
More proposals:
  • Graph Library: Overview - P3126R3 (2025-04-13)
  • Graph Library: Algorithms - P3128R3 (2025-04-13)
  • Graph Library: Graph Container Interface - P3130R3 (2025-04-13)
  • Graph Library: Graph Containers - P3131R3 (2025-04-13)
2D Graphics Early development. Draft P0267R10 (2019-10-07).

See also

C documentation for Experimental C features

External links

1. PL22.16/WG21 document list - All C++ committee documents (TS/proposals) for 2016-2025.
2. JTC1/SC22/WG21 Proposals (mailing) for 2025 .